/*
 * Copyright (c) 2011 The Boeing Company
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Gary Pei <guangyu.pei@boeing.com>
 */
#include "lr-wpan-error-model.h"

#include <ns3/log.h>

#include <cmath>

namespace ns3
{

NS_LOG_COMPONENT_DEFINE("LrWpanErrorModel");

NS_OBJECT_ENSURE_REGISTERED(LrWpanErrorModel);

TypeId
LrWpanErrorModel::GetTypeId()
{
    static TypeId tid = TypeId("ns3::LrWpanErrorModel")
                            .SetParent<Object>()
                            .SetGroupName("LrWpan")
                            .AddConstructor<LrWpanErrorModel>();
    return tid;
}

LrWpanErrorModel::LrWpanErrorModel()
{
    m_binomialCoefficients[0] = 1;
    m_binomialCoefficients[1] = -16;
    m_binomialCoefficients[2] = 120;
    m_binomialCoefficients[3] = -560;
    m_binomialCoefficients[4] = 1820;
    m_binomialCoefficients[5] = -4368;
    m_binomialCoefficients[6] = 8008;
    m_binomialCoefficients[7] = -11440;
    m_binomialCoefficients[8] = 12870;
    m_binomialCoefficients[9] = -11440;
    m_binomialCoefficients[10] = 8008;
    m_binomialCoefficients[11] = -4368;
    m_binomialCoefficients[12] = 1820;
    m_binomialCoefficients[13] = -560;
    m_binomialCoefficients[14] = 120;
    m_binomialCoefficients[15] = -16;
    m_binomialCoefficients[16] = 1;
}

double
LrWpanErrorModel::GetChunkSuccessRate(double snr, uint32_t nbits) const
{
    double ber = 0.0;

    for (uint32_t k = 2; k <= 16; k++)
    {
        ber += m_binomialCoefficients[k] * exp(20.0 * snr * (1.0 / k - 1.0));
    }

    ber = ber * 8.0 / 15.0 / 16.0;

    ber = std::min(ber, 1.0);
    double retval = pow(1.0 - ber, nbits);
    return retval;
}

} // namespace ns3
